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Monday, 24 October 2011

Cohesion, collaboration and clinical impact are
the watchwords of a new phase of stem cell research in Cambridge, UK

Monday, 24 October 2011

Few
areas of research have been surrounded by such hope – and such hype – as stem
cell biology. With their unique capacity to renew themselves and to give rise
to the body’s many different cell types, stem cells have the potential to
repair tissues damaged by disease or trauma: from a failing heart to lost nerve
cells.

Rosettes of human, patient-specific

neural stem cells. Credit: Rick Livesey

and Yichen Shi.

But the
route from the laboratory to the clinic is a long one. Before patients can be
treated, many years of fundamental research and clinical testing have to take
place.

“Cambridge is one of the few places in the
world that has a critical mass in both basic stem cell science and medical
translation.”

Since
2007, the University has invested over £38 million in laboratories and posts,
and has prioritised stem cell biology as a Strategic Research Initiative. There
are now 26 stem cell laboratories across the University, which have attracted
some £95 million in funding. Many of the researchers are hosted by the WT
Centre and the University’s Medical
Research Council (MRC) Laboratory for Regenerative Medicine (established by
Professor Roger
Pedersen), which focus on fundamental and translational stem cell research,
respectively.

Now, a
major effort is under way to draw together stem cell research across the
University into a new Stem Cell Institute (SCI). The SCI currently spans
several sites but the intention is to bring all these groups together
ultimately in a major new research institute on the Cambridge Biomedical
Campus. Unification will create the ideal stage for the translation of
fundamental research into clinical benefits – research such as the long-running
programme led by Professor Robin Franklin in the Department of Veterinary
Medicine, whose work on multiple sclerosis is about to move into clinical
trials (see below).

“Collaboration has always happened in
Cambridge,” explained
Professor Smith, “but pulling people
together will capitalise fully on the rich opportunities. SCI will provide a
unified organisation and a strategic direction for stem cell research that
starts from basic science but sets clinical delivery and interaction with bio
industry firmly in its sights.”

A key
component will be interdisciplinary research teams that link stem cell biology
with molecular disease mechanisms through to clinical applications.

Alongside
Professor Smith in spearheading the reshaping will be the newly established
Chair of Stem Cell Medicine, to which Professor Oliver Brüstle has been
elected. Professor Brüstle is currently Director of the Institute of
Reconstructive Neurobiology at the University Of Bonn, Germany, and an expert
in stem cells of the nervous system and their application in neurodegenerative
disease.

Professor
Brüstle – who notably fought for legalisation of research on human embryonic
stem (ES) cells in Germany and finally became the first scientist to obtain a
respective license – regards stem cell therapies as “just another way to treat disease”. He is at pains to emphasise
that cell transplantation is not the only way that stem cells can bring
clinical benefit.

“In fact, a much closer prospect is the use of
stem cells to study specific diseases in the laboratory and to develop new
drugs.”

Another
important opportunity is the possibility of improving cancer treatment by
identifying and targeting tumour stem cells.

“Of course there are challenges to overcome
before stem-cell-based medicine is commonplace,” added Professor Brüstle.

“For example, we need to learn more about how
human ES cells differ from mouse ES cells, and how their fate is controlled.”

In
fact, a major discovery about the differences between human and mouse ES cells
was made in Cambridge. Professor Pedersen and Dr Ludovic
Vallier and colleagues showed that human ES cells represent a
developmentally more mature stage than naive mouse ES cells. This can explain
why some procedures for producing specific cell types from mouse ES cells do
not work well with human cells.

“Human ES cells are less versatile. This
research has changed the way stem cell researchers think about human ES cells,” explained Professor Smith.

The
goal now is to understand this difference at a molecular level. Professor Azim Surani at the WT/Cancer
Research UK Gurdon Institute in Cambridge has pioneered a deep-sequencing
technique to do precisely this. His team can now analyse the entire
transcriptome (all the gene products) in a single stem cell, opening the door
not only to understanding the specific nature of human ES cells but perhaps
also to how to make them more like mouse cells.

Professor
Smith foresees a time when stem cells will permeate all areas of biology.

“Stem cells are going to be instrumental in
taking us to the next level of understanding about how cells make decisions
about their fate. Increasingly, we’ll see them being used in laboratories as
systems to look at basic biological questions that may have nothing directly to
do with stem cell biology. Stem cells will soon become the research tool of
choice in mammalian cell biology.”

Self-service
brain repair in multiple sclerosis (MS)

Researchers
led by Professor Robin Franklin at the MS Society Cambridge Centre for Myelin
Repair recently discovered a molecule that is capable of activating the brain’s
own stem cells to repair damage caused by MS. Now, preparations have begun for
a small-scale trial to test whether this process can regenerate lost nerve
function, for which there is currently no treatment available.

Nerve
fibres are progressively damaged in MS because they lose a protective coating
of myelin when the cells that make it (the oligodendrocytes) are destroyed by
the body’s immune system. The aim of the new treatment will be to stimulate
stem cells that occur naturally in the brain and which have the ability to
regenerate lost oligodendrocytes.

In the
course of over two decades of research, Professor Franklin and colleagues have
found that one of the major problems in MS is that the patient’s stem cells
lose the ability to become normal oligodendrocytes. When oligodendrocytes are
destroyed during the MS disease process, they are not replenished from the
brain’s pool of stem cells. But the ability can be regained when the patient’s
stem cells are activated through the retinoid acid receptor RXR-γ, as shown in
collaboration with colleagues in Edinburgh using animal models and published in
Nature Neuroscience in January 2011.

The
discovery was a landmark moment in the search for treatments for MS, as
Professor Franklin explained.

“If we can encourage the patient’s own stem
cells to develop into oligodendrocytes and replace the lost myelin, then this
might restore the nerve functions lost in MS.”

The
idea behind the proposed treatment is not only to repair the damage but also to
arrest any further damage caused by the patient’s immune system. An effective
treatment for halting the destruction of oligodendrocytes, alemtuzumab
(Campath), was developed in Cambridge by Professor Alastair Compston and Dr
Alasdair Coles at the Department of Clinical Neuroscience.

The
prospective new trial, which is currently being designed by Dr Coles together
with colleagues at University College London and the University of Edinburgh,
and is not yet recruiting patients, plans to use a licensed drug, bexarotene,
which activates RXR-γ.

Professor
Franklin added: “Essentially, the
philosophy of our approach is not to transplant stem cells from elsewhere but
to encourage the patient’s own stem cells to do the work of repairing the
damaged tissue.”

Monday, 10 October 2011

Researchers from the Wellcome Trust Sanger Institute have today announced
a new technique to reprogram human cells, such as skin cells, into stem cells.
Their process increases the efficiency of cell reprogramming by one
hundred-fold and generates cells of a higher quality at a faster rate.

Until now cells have been reprogrammed
using four specific regulatory proteins. By adding two further regulatory
factors, Liu and co-workers brought about a dramatic improvement in the
efficiency of reprogramming and the robustness of stem cell development. The
new streamlined process produces cells that can grow more easily.

"This
research is a milestone in human stem cells,"
explains Wei Wang, first author on the research from the Wellcome Trust Sanger
Institute.

"Our
technique provides a foundation to unlock the full potential of stem
cells."

Stem cells are unspecialized cells that
are able to renew themselves through cell division and can be induced to become
functional tissue- or organ-specific cells. It is hoped that stem cells will be
used to replace dying or damaged cells with healthy, functional cells. This
could have wide-ranging uses in medicine such as organ replacement, bone
replacement and treatment of neurodegenerative diseases.

With more than 20 years of research,
gold standard stem cells are derived from mice, largely because they are easy
to work with and provide accurate and reproducible results. The team's aim was
to develop human cells of equivalent quality to mouse stem cells.

"The
reprogrammed cells developed by our team have proved to have the same
capabilities as mouse stem cells," states
Pentao Liu, senior author from the Sanger Institute.

Retinoic acid
receptor gamma (RAR-γ) and liver receptor
homolog (Lrh-1), the additional regulatory factors used by Liu and
co-workers, were introduced into the skin cells along with the four other
regulatory proteins. The team's technology produced reprogrammed cells after
just four days, compared to the seven days required for the four-protein
approach. Key indicators of successfully reprogrammed cells, Oct4 and Rex-1
genes, were seen to be switched on much faster in a much higher number of
cells, demonstrating increased efficiency in reprogramming.

"This
is the most promising and exciting development in our attempt to develop human
stem cells that lend themselves in practical applications. It bears comparison
to other technologies as it is simple, robust and reliable," says Allan Bradley, Senior Group Leader and Director of Emeritus at
Sanger Institute.

Friday, 7 October 2011

Investigators at the Massachusetts General Hospital (MGH)
Center for Regenerative Medicine and the Harvard Stem Cell Institute (HSCI)
have found that Sox2 – one of
the transcription factors used in the conversion of adult stem cells into
induced pluripotent stem cells (iPSCs) – is expressed in many adult tissues
where it had not been previously observed. They also confirmed that
Sox2-expressing cells found in the stomach, testes, cervix and other structures
are true adult stem cells that can give rise to all mature cell types in those
tissues. The study appears in the October issue of Cell Stem Cell.

"We
have known that Sox2 is essential for maintaining pluripotency in embryonic
stem cells and neural stem cells and, with three other embryonic genes, is
sufficient to convert adult cells into iPSCs," says Konrad
Hochedlinger, PhD, of the MGH Center for Regenerative Medicine and HSCI,
who led the study.

"Our
study shows that Sox2 is a much more widespread marker of adult stem cells and
suggests these cells may share common genetic programs to maintain stem cell
fate, findings that could be exploited to amplify or modify these cells for
applications in regenerative medicine."

Hochedlinger's team set out to
investigate whether genes known to be important to pluripotent stem cells –
cells that can give rise to several different types of tissue – also play a
role in adult stem cells, which maintain populations of particular types of
tissue. Sox2 is one of four embryonic genes that are required to be expressed
for the generation of iPSCs – which have many of the characteristics of
embryonic stem cells – but the other three genes are not expressed in adult
stem cells. Sox2 is known to be expressed at the very earliest stages of
embryonic development and to play a role in development of several types of
fetal tissue. But prior to this study, its expression had been observed in only
a few types of adult tissues.

In a series of experiments with mice,
the researchers first showed that Sox2 continues to be expressed in specific
populations of adult cells of the stomach, esophagus, testes, cervix, anus and
the lens of the eye. These Sox2-expressing cells were proven to be able both to
replenish their population and to give rise to the fully differentiated cells
found within the particular tissue, confirming their status as adult stem
cells.

Additional findings revealed that fetal
tissues expressing Sox2, which are at a stage before the appearance of true
stem cells, will develop into tissues that include Sox2-expressing adult stem
cells and that Sox2 appears to be the only transcription factor expressed in
stem cells at all stages of development – embryonic, fetal and adult. However,
Sox2 expression has never been found in muscle or connective tissue, blood
cells, or in organs such as the heart or kidney, indicating that other factors
must play a similar role in those tissues.

"Adult
stem cells are difficult to isolate and manipulate, so the fact that Sox2
appears to be a marker for many adult stem cells may allow researchers to
isolate them more easily and study them in more detail," Hochedlinger explains.

"Manipulation
of Sox2 expression could help us push embryonic stem cells into particular
types of adult stem cells and, when combined with certain growth factors,
induce differentiation into desired types of tissue. All of these possibilities
need to be investigated."

Hochedlinger is an associate professor
of Medicine at Harvard Medical School and a Howard Hughes Medical Institute
Early Career Scientist.

Stem cells made by reprogramming
patients' own cells might one day be used as therapies for a host of diseases,
but scientists have feared that dangerous mutations within these cells might be
caused by current reprogramming techniques. A sophisticated new analysis of
stem cells' DNA finds that such fears may be unwarranted.

Kristin Baldwin, Ph.D., is an associate

professor in the Scripps Research

Institute's Dorris Neuroscience

Center. Credit: photo courtesy of

The Scripps Research Institute.

"We've
shown that the standard reprogramming method can generate induced pluripotent
stem cells that have very few DNA structural mutations, which are often linked
to dangerous cell changes such as tumorigenesis," said Kristin
Baldwin, associate professor at The Scripps
Research Institute's Dorris Neuroscience Center and a senior author of the
report, which appears in the October 7, 2011 issue of the journal Cell Stem
Cell. For this study the Baldwin lab collaborated with a genomics and
bioinformatics expert, Ira M. Hall, an assistant professor of biochemistry and
molecular genetics at the University of Virginia who is co-senior author.

The induced pluripotent stem cell
(iPSC) technique was first described in 2006. It requires the insertion into an
ordinary non-stem cell of four special genes, whose activities cause the cell
to revert to a state like that of embryonic stem cell. In principle, iPSCs may
be used to repair diseased or damaged tissues, and because they are made from a
patient's own cells, they shouldn't provoke an immune reaction. But recent
studies have found unacceptably high levels of mutations in iPSCs derived from
adult human cells. That has led to widespread suspicion that the reprogramming
process is largely to blame.

In the new study, the Scripps Research
and University of Virginia researchers set out to investigate this issue using
the latest chromosomal error-mapping methods.

"The
techniques that our University of Virginia colleagues brought to this study are
much more sensitive than anything else that's available right now," said Michael J. Boland, a research associate in the Scripps
Research Baldwin lab and co-first author of the paper with Aaron R. Quinlan, a
postdoctoral researcher in Hall's lab. The new methods included a
high-resolution version of a DNA-error-finding technique known as paired-end
mapping, and an advanced algorithm, "HYDRA," for handling the
voluminous mapping data.

To generate the iPSCs, the Scripps
Research team followed the standard, four-gene reprogramming procedure, but
sought to minimize other potential sources of DNA mutations that might have
influenced some previously reported results. The donor cells they selected were
not decades-old human skin cells, but relatively error-free fibroblast cells
from fetal mice. The researchers also kept these fibroblast cells only briefly
in lab dishes before reprogramming them.

When the team members analyzed these
iPSCs they used two strategies to distinguish which mutations were present in
rare donor fibroblast cells and which were newly acquired during reprogramming.
Their advanced techniques also allowed them to find more kinds of mutations,
across a wider range of the genome, than ever before. Yet instead of finding
more mutations, they found almost none.

"We
sequenced three iPSC lines at very high resolution, and were surprised to find
that very few changes to the chromosomal sequence had appeared during
reprogramming," said Boland.

Each of the iPSC lines contained only a
single mutation that probably originated from the reprogramming process; two
affected genes while the other appeared not to. Mutations inherited from the
donor fibroblast cell were present in one pair of lines, while a second line "inherited" none. The
researchers were particularly cheered by the complete absence of new "retro-element transpositions"
— mutations caused by retrovirus-like sequences that burrowed into the
mammalian genome long ago that can become active again in certain cell types.
All cells have ways to suppress these retro-elements, but the suppression
mechanisms in normal cells are different from those in stem cells, so the
researchers had worried that retro-elements would be allowed to escape suppression
during the transition to a stem cell state. While no previous surveys of iPSCs
could detect these mutations, this study showed that despite very sensitive
detection of controls, no retro-elements had become active during
reprogramming.

"That
was is very encouraging, because retro-element mutations can be very damaging
to the genome," Boland said.

Some of the mutations seen in human
iPSCs in previous studies might have been due to incomplete reprogramming that
impaired the cells' DNA-maintenance mechanisms. In this study using mouse
iPSCs, however, there was no doubt that a complete reprogramming to an
embryonic state had occurred: all three iPSC lines were used to produce live,
fertile mice, in work that Boland, Baldwin, and their colleagues described in
Nature in 2009.

"The
mice generated from these cells have survived to a normal lab-mouse lifespan
without obvious diseases that might arise from new DNA mutations," said Baldwin.

Her lab now is trying to determine
whether a reprogramming method similar to the one used with mouse iPSCs in this
study could also yield relatively error-free human iPSCs.

"If
our results with these mouse cells are applicable to human cells, then
selecting better donor cells and using more sensitive genome-survey techniques should
allow us to identify reprogramming methods that can produce human iPSCs that
will be safer or more useful for therapies than current lines," she said.

Wednesday, 5 October 2011

A technique called somatic-cell nuclear transfer
(cloning) has been applied to human oocytes, resulting in the generation of
personalized stem cells, albeit genetically abnormal ones.

Wednesday, 05 October 2011

A team of scientists led by Dieter Egli
and Scott Noggle at The New York Stem Cell Foundation (NYSCF) Laboratory in New
York City have made an important advance in the development of patient-specific
stem cells that could impact the study and treatment of diseases such as
diabetes, Parkinson’s, and Alzheimer’s. As reported in today’s Nature, for the
first time the scientists have derived embryonic stem cells from individual
patients by adding the nuclei of adult skin cells from patients with type-1 diabetes
to unfertilized donor oocytes. However, this technique creates triploid human pluripotent
stem-cell lines.

The achievement is significant because
such patient-specific cells potentially can be transplanted to replace damaged
or diseased cells in persons with diabetes and other diseases without rejection
by the patient’s immune system. The scientists report further work is necessary
before such cells can be used in cell-replacement medicine.

The research was conducted in The NYSCF
Laboratory in Manhattan in collaboration with clinicians and researchers at
Columbia University Medical Center. DNA analysis was provided by scientists at
the University of California, San Diego.

“The
specialized cells of the adult human body have an insufficient ability to
regenerate missing or damaged cells caused by many diseases and injuries,” said Dr. Egli, NYSCF senior scientist in the study.

“But
if we can reprogram cells to a pluripotent state, they can give rise to the
very cell types affected by disease, providing great potential to effectively
treat and even cure these diseases. In this three-year study, we successfully
reprogrammed skin cells to the pluripotent state. Our hope is that we can
eventually overcome the remaining hurdles and use patient-specific stem cells
to treat and cure people who have diabetes and other diseases.”

“The
ultimate goal of this study is to save and enhance lives by finding better
treatments and eventually cures for diabetes, Alzheimer’s, Parkinson’s and
other debilitating diseases and injuries affecting millions of people across
the US and the globe,” said NYSCF CEO Susan L. Solomon.

“This
research brings us an important step closer to creating new healthy cells for patients
to replace their cells that are damaged or lost through injury.”

The scientists demonstrate for the
first time that the transfer of the nucleus from an adult skin cell of a
patient into an oocyte without removing the oocyte nucleus results in
reprogramming of the adult nucleus to the pluripotent state. Embryonic stem
cell lines were then derived from the oocyte containing the patient’s genetic
material.

Since these pluripotent stem cells also
have a copy of the chromosome from the oocyte, resulting in an abnormal number
of chromosomes, these cells are not ready for therapeutic use. Future work will
focus on understanding the role of the oocyte chromosome so that patient
specific stem cells can be made that contain only the patient’s DNA.

In the study, skin cells from patients
with type-1 diabetes and healthy patients (control group) were reprogrammed,
allowing the derivation of pluripotent stem cells, cells that have the capacity
for universal tissue production. Such cells potentially could be used to create
beta cells that produce insulin.

“This
is an important step toward generating stem cells for disease modeling and drug
discovery, as well as for ultimately creating patient-specific cell-replacement
therapies for people with diabetes or other degenerative diseases or injuries,” said Rudolph L. Leibel, MD, co-director of Columbia’s Naomi Berrie
Diabetes Center and a collaborator in the study.

The study raises the possibility of
using somatic cell reprogramming to create banks of stem cells that could be
used for a wide range of patients, noted another collaborator, Robin Goland, MD,
co-director of the Naomi Berrie Diabetes Center.

“In
theory, stem cell lines could be matched to a particular patient, much as we do
now when we screen an individual for compatibility with a kidney transplant,” she said.

“This
project is a great example of how enormous strides can be achieved when
investigators in basic science and clinical medicine collaborate,” said Mark V. Sauer, MD, a coauthor of the paper and Vice Chairman
of the Department of Obstetrics and Gynecology and chief of reproductive
endocrinology at Columbia University Medical Center. Dr. Sauer is also program director
of assisted reproduction at the Center for Women’s Reproductive Care.

“I
feel fortunate to have been able to participate in this important project.”

Zach W. Hall, PhD, former Director of
the NIH’s National Institute of Neurological Disorders and Stroke and former
President of the California Institute for Regenerative Medicine said:

“This
work represents a major advance toward the production of patient-specific stem
cells for therapeutic use by demonstrating that the nucleated oocyte has the
ability to completely reprogram the nucleus of an adult human cell.”

The study was funded solely with
private funding and adhered to ethical guidelines adopted by the American
Society for Reproductive Medicine and the International Society for Stem Cell Research,
as well as protocols reviewed and approved by the institutional review board
and stem cell committees of Columbia University.

The New York Stem Cell Foundation (NYSCF) conducts advanced stem cell research in its own laboratory
and supports research by stem cell scientists at other institutions around the world.
More information is available at www.nyscf.org.

Columbia University Medical Center (CUMC) provides international leadership in basic, pre-clinical and
clinical research, in medical and health sciences education, and in patient
care. More information is available at www.cumc.columbia.edu.